RAV4 Hybrid P0A80: what "replace hybrid battery" really means, and the cheaper checks to do first

The code sounds final. In practice the pack has a few common failure points that cost far less than a battery, and the newer packs each fail differently.

The hybrid battery ECU watches the voltage of each cell block during charge and discharge. When one block sags more than the others, it stores P0A80 and reduces how hard it works the pack. A weak block can be genuinely worn, but also just hot, because a clogged cooling fan makes one corner of the pack age faster.